1. Field of the Invention
The present invention relates to denture adhesives containing a polymeric activator, such as a polymeric acid, and to methods of improving a denture adhesive product by adding a polymeric activator.
2. Description of the Related Art
Dentures are substitutes for missing teeth and serve as replacement for all or some of the teeth found in the oral cavity. Despite diligent efforts by dental professionals and designers of dental prostheses, dentures do not always fit perfectly. Over time, even well-fitting dentures can become ill-fitting due to natural shrinkage and changes in the gum or mucous tissues. Therefore, adherent creams, liquids or powders are often used to secure dentures within the mouth.
There are a number of desirable characteristics of a denture fixative composition. One extremely desirable attribute is that it develops a high degree of tack upon contact with saliva so that the dentures can be held in place as soon as they are seated in the mouth. It is also highly desirable that the mucilage be spread over the denture-mucosa interface in order to effectively seal the denture in place and that the mucilages possess sufficient cohesive strength to withstand the stresses of mastication which act to rupture the seal and thus dislodge the denture. The denture fixative must also exhibit sufficient resistance to degradation under the extreme environmental changes that occur in the oral cavity during such common actions as drinking coffee or other hot beverages. Of course, the adhesive must also be releasable so that the denture wearer may remove the dentures for cleaning and maintenance. Denture adhesives are generally sold as a cream, liner or strip, liquid or powder, and many examples are well known in the art.
Early denture adhesives contained finely ground particles of natural gums that expanded when wet with water to become a viscous gel, which acted as a cushion and an adherent between the denture plate and the gum tissue. These denture adhesives, however, have tended to be supplanted by polymeric denture adhesives.
U.S. Pat. No. 3,003,988, for example, describes a dental fixative composition in which the dental fixative is a mixed partial salt containing calcium cations and alkali or quaternary ammonium cations of a lower alkyl vinyl ether-maleic anhydride type copolymer. The mixed salt copolymer is stated to be a water-insoluble, but water sensitized, copolymer.
U.S. Pat. No. 3,736,274 teaches a dental fixative composition that contains a lower alkyl vinyl ether-maleic anhydride polymeric material, a polymeric N-vinyl lactam and a sodium carboxymethyl cellulose. The carboxymethyl cellulose prevents the lower alkyl vinyl ether-maleic anhydride copolymer-N-vinyl lactam complex from completely precipitating when placed in water.
U.S. Pat. No. 3,868,432 teaches an anhydrous denture adhesive composition that is a mixture of a copolymer of an acrylamide and an anionic synthetic gum component which can be a copolymer of maleic acid with vinyl lower alkyl ether.
U.S. Pat. No. 4,373,036 discloses a denture fixative composition containing hydroxypropyl cellulose and a partially neutralized, optionally crosslinked, polyacrylic acid or a precursor combination thereof, or partially neutralized copolymers of maleic acid or anhydride and alkyl vinyl ethers which are optionally partially crosslinked, or a precursor combination thereof, and/or polyethylene oxide.
U.S. Pat. No. 4,521,551 discloses a denture fixative composition containing denture fixative excipients and as the denture fixative, a water soluble partially neutralized alkyl vinyl ether-maleic acid or anhydride copolymer, optionally partly crosslinked with a polyhydroxyl compound, and at least one hydrophilic polymer, preferably sodium carboxymethyl cellulose, polyethylene oxide or hydroxy propyl sugar.
U.S. Pat. No. 4,758,630 discloses denture adhesives comprising zinc and strontium partial salts of lower alkyl vinyl ether-maleic acid copolymers, wherein the zinc and strontium cations are unmixed with any other cations or ester functions in the copolymeric salt, the remaining initial carboxyl group being unreacted.
U.S. Pat. No. 5,006,571 discloses denture adhesives comprising a substantially anhydrous mixture of a mixed Na/Ca salt of methyl vinyl ether-maleic acid, sodium carboxymethyl cellulose, and a trivalent cation. Dihydroxy aluminum sodium carbonate may be the source of the trivalent cation. Dihydroxy aluminum sodium carbonate may be the source of the trivalent cation, in which case a food grade acid must be added to aid in release of the aluminum from the composition. Exemplary acids include citric acid, malic acid, tartaric acid, and fumaric acid. The acid may comprise up to about 4 percent by weight of the denture adhesive composition. Additionally, benzoic acid or sorbic acid may be included in the denture adhesive as a preservative.
U.S. Pat. Nos. 5,525,652 and 5,830,933 disclose the use of mixed copolymer acid salts in the formulation of denture adhesive compositions. Preferably the salts are mixed salts of Ca/Na or Ca/K, and most preferably they are partial Zn/Mg salts and Na/Zn/Mg salts. The disclosure of each of these is hereby incorporated by reference.
U.S. Pat. No. 5,093,387 also discloses that benzoic acid and sorbic acid may be used as preservatives in denture adhesive formulations in amount of about 0.03 to about 0.6 percent by weight of the total denture adhesive composition.
Each of the denture adhesive materials discussed above has certain advantages and disadvantages when compared with other denture adhesives. The search for better denture adhesive materials continues, however, and denture adhesives with better hold, longer hold and better organoleptic properties are always desirable.